In the processing and handling of aggregate materials such as sand, gravel or crushed stone, as well as in related industrial materials like coal, slag, iron ore, phosphate, potash, primary metal and related chemical industries, it is necessary to utilize relatively large quantities of water or other liquids in conjunction with or as a dispersing medium for finely sized solid particles produced in the respective grading, concentration or other process. At some point in the process, it is usually necessary to subsequently effect a separation or dewatering of these fine solid materials from the slurry containing them.
One method of dewatering fine granular material prior to disposing of the waste water or other liquid has been to subject the mixture to suitable dewatering devices. The most widely employed method for dewatering in the mineral aggregates industry is an inclined screw dehydrator, which slowly moves the solid material up the incline of the screw thread out of a feed basin permitting back flow of the water to waste. However, such equipment has limited water handling capacity and is plagued by the loss of valuable fines that are carried away in the back flow.
Another technique involves the use of centrifugal force to remove the free moisture. However, the high cost, high power consumption, and wear characteristics associated with such a centrifuge apparatus have prevented the wide use of that technique on a commercial basis for handling abrasive materials. Similarly, the use of pressure or vacuum filters has not been commercially attractive, particularly for the sand and gravel and crushed stone industries.
Another common technique employed for dewatering fine particle slurries is the use of vibrating dewatering screens. The deck of these screens has often taken the form of finely woven wire cloth through which material may pass. Some have in recent times used urethane decks with small openings for water to pass. However the typical horsepower consumption of a dewatering screen system is high. Moisture content may vary by particle size and mineral composition.
Furthermore, many of these machines used to dewater the aggregate product are expensive and already in place. It is not cost effective to replace entire systems with systems such as those disclosed in U.S. Pat. No. 8,695,804, which is hereby incorporated by reference in its entirety.
As such, there is a need in the art for a drop in or retro-fit unit that can be used with one or more of the existing machines to provide for a dewatering device and recycle device to dry aggregate product and to recycle fine materials that may pass unwanted through a vibrating screen or other drying member.